Crematogaster obscurata is a small (~2.3 mm) reddish brown arboreal species with a darker face and gaster, a trapezoidal petiole, and abundant flattened, semierect hairs dispersed across its head, mesosoma and gaster. The species is part of a complex of xerophilic species that occurs throughout the Neotropics (Longino, 2003), and has established a single introduced population in Florida (Deyrup, 2007; Deyrup et al., 2000). Crematogaster obscurata is treated in Longino’s (2003)revision, and Deyrup (2007)reviewed its identification, ecology and candidacy for eradication in Florida. The species is considered innocuous in both its native and introduced range.
In its native habitat in Costa Rica, Crematogaster obscurata occurs in dry forest habitats and beach margins, where it has been collected from trees (Longino, 2003). In Florida the species was first collected in 1995 and first reported as C. agnita Wheeler (Deyrup et al., 2000), which was subsequently synonymized with C. obscurata (Longino, 2003). Nests were found in dead portions of living trees, including hollow twigs and branches, and insect galleries in larger dead branches (Deyrup, 2007). One nest was in the stub of a dead branch of Piscidia piscipula (L.) Sargent, the others in Rhizophora mangle L. The discovery of two nests in separate red mangrove tress, each isolated in the intertidal zone, suggested to Deyrup that foragers might be confined to single trees. Having observed multiple dealate queens within collected nests, he also proposed that the species produces polygynous colonies capable of spreading by fission.
Deyrup presents arguments for and against the eradication of the single known C. obscurata population. On one hand, the species is apparently innocuous, hasn’t spread in the 11 years since first detected in Florida, and the need to unequivocally verify its status as introduced. On the other hand, the Florida C. obscurata population might eventually become more pernicious through ecological release, would be relatively easy to eradicate, and was likely introduced from Central America, possibly in association with the ornamental plant trade. Two US port of entry interception records of the species on Oncidium orchids from Guatemala (Longino, 2003)give credence to this last scenario.
Not considered a significant pest species.
Diagnosis of worker among Antkey species. Head shape ovoid. Antenna 11-segmented. Antennal club 2-segmented. Antennal scapes not conspicuously short; easily extended beyond eye level. Antennal scrobe lacking. Eyes medium to large (greater than 6 facets) but distinctly less than half head length. Mandibles triangular. Pronotal spines absent. Propodeum armed with spines or teeth. Waist 2-segmented. Petiole flattened; lacking a distinct node; lacking peduncle; lacking large subpetiolar process. Petiole shape subtriangular with the dorsal profile sloping anteriorly. Postpetiole attached to upper surface of gaster. Head and mesosoma with abundant short flattened, semierect hairs.
This species may be distinguished from other Florida Crematogaster by its flattened, semierect hairs and by its granulate microsculpture on the sides of the head, mesopleura and propodeum. It can be separated from Crematogaster scutellaris, another commonly intercepted species, by the following characters: (1) a 2-segmented club (versus 3-segmented); (2) a more triangular petiole (versus trapezoidal); (3) abundant, flattened semierect hairs on its dorsal surfaces; (4) head not often a reddish color that contrasts with rest of body.
Crematogaster scutellaris
Native Range. Mexico, Guatemala, Belize, Costa Rica, and Venezuela (Longino 2003).
Introduced Range. USA: Florida (Summerland Key, Monroe County).